Hybrid electric vehicles use an internal combustion engine and electric motors for propulsion. The electric motors can be powered by a battery that is usually at a high voltage, such as 200-300 volts. The battery and the electric motors can be electrically connected to each other by a high voltage bus that carries current from the battery to the electric motor and/or to other components of the vehicle. The high voltage bus and the battery can be connected through a main contactor during normal operation of the vehicle.
Prior to normal operation of the vehicle, the high voltage bus may be at a voltage less than the voltage of the battery. When normal operation of the vehicle is desired, the high voltage bus is typically precharged by connecting the high voltage bus to the battery through a precharge contactor and a resistor, so that the voltage of the high voltage bus is brought up to the voltage of the battery within a certain tolerance, such as 10 V. After the high voltage bus is precharged, a main contactor can be closed to directly connect the battery to the high voltage bus. However, while this type of precharging brings the voltage of the high voltage bus close to the voltage of the battery, the high voltage bus may not be precharged in the quickest, most efficient, and optimal way.
Accordingly, there is an opportunity for systems and methods for precharging a high voltage bus with a uniform current through the use of relatively inexpensive components while allowing the high voltage bus to be fully charged in a quick, efficient, and optimal way.